A method to operate and control one example of an electrically controlled actuator is described in U.S. Pat. No. 5,494,219. This patent presents a method for controlling opening and closing coils of a dual coil fuel injector. The opening and closing coils are used to create electromagnets that may be made to open and close the fuel injector during engine operation. An injector opening cycle is described by a sequence where current is supplied to the closing coil before current is applied to the opening coil. Current is applied to the closing coil with the objective of overcoming residual magnetism that remains in the closing electromagnet core. By attempting to overcome the residual magnetism, the method seeks to negate the latching effect that the residual magnetism provides between the electromagnet and the armature.
The above method also has several disadvantages. For example, the method simply recognizes that it can be desirable to cancel the residual magnetism in an electromagnet's core when the core has been exposed to a magnetic field. In other words, the method does not recognize or provide for reducing and/or counteracting residual magnetism that can result from other sources. Further, the method does not recognize or describe how to reduce sources of residual magnetism that may be present in other fuel injector components. As a result, the above-mentioned method may only cancel a fraction of the residual magnetism present in a fuel injector. Consequently, the underlying residual magnetism may make it necessary to use additional current to restart the fuel injector after the engine has been stopped. The additional current can strengthen a magnetic field so that the injector armature is moved to a desired position, but it can also lead to degraded injector performance under some conditions.